First-line tislelizumab and ociperlimab combined with gemcitabine and cisplatin in advanced biliary tract cancer (ZSAB-TOP): a multicenter, single-arm, phase 2 study.

Adding a PD-1/PD-L1 inhibitor to gemcitabine plus cisplatin (GemCis) has shown survival benefits in advanced biliary tract cancer (BTC). Dual inhibition of PD-1/PD-L1 and TIGIT may act synergistically, and further enhance antitumor effects. ZSAB-TOP was a single-arm, multicenter, phase 2 study (NCT05023109) evaluating efficacy and safety of first-line tislelizumab (a PD-1 inhibitor) plus ociperlimab (a TIGIT inhibitor) and GemCis in advanced BTC. Eligible patients received tislelizumab (200 mg) and ociperlimab (900 mg) on day 1 until unacceptable toxicity or disease progression, in combination with cisplatin (25 mg/m²) and gemcitabine (1000 mg/m²) on days 1 and 8 of a 21-day cycle for a maximum eight cycles. The primary endpoint was confirmed objective response rate (ORR) evaluated by the investigator, which was compared with a historical ORR of 25% with GemCis, with a statistical superiority setting at p ≤ 0.05. From March 8, 2022, to January 18, 2023, 45 patients were enrolled. Among the 41 patients in the efficacy analysis set, the confirmed ORR was 51.2% (95% CI 35.1-67.1), achieving the statistical superiority criteria (p = 0.0003). Patients who had TIGIT/PD-L1 (n = 16) tended to have a numerically greater confirmed ORR (75.0% [95% CI 47.6-92.7]). After a median follow-up of 14.6 months, median progression-free survival was 7.7 months (95% CI 6.0-9.4), with a median overall survival of 17.4 months (95% CI 11.7-not reached). Treatment-related adverse events of grade ≥3 occurred in 60.0% of patients; immune-mediated adverse events of any grade was observed in 42.2%, with the majority being grade 1 or 2. In conclusion, first-line tislelizumab and ociperlimab plus GemCis yielded clinically promising tumor response and survival outcomes in advanced BTC and were generally well tolerated without new safety signals.